The objective of the Pharmacokinetics and Pharmacodynamics (PK/PD) Services Core will be to provide centralized support for the PK and key PD analyses common to preclinical macaque studies in Project 2 and human clinical studies in Project 3, thereby ensuring Program's research integrity and comparability between the preclinical and clinical studies proposed. To this end, we will provide the following functions. (1) We will validate the quality of a griffithsin (GRFT) reference standard. A series of biochemical, biophysical and virological assays will be used to validate the quality of GRFT. (2) We will develop an immunoassay to validate the potency of GLP/GMP-manufactured GRFT. Upon validation of the assay at OCRP, its standard operating procedure will be transferred to Project 1 and Core B. (3) We will detect and quantify GRFT active pharmaceutical ingredient (API) and GRFT-binding antibodies in biological fluids to support PK/PD analysis in Projects 2 and 3. In addition to conventional methods based on enzyme-linked immunosorbent assays, we will develop surface plasmon resonance-based analytical methods to detect low-affinity, rapidly dissociating antibodies. As part of PK assessment, we will use HIV-1 neutralization and cell-cell fusion assays to measure the anti-HIV-1 capacity of rectal fluid samples. (4) We will analyze the impact of GRFT gel treatment on the mucosal environment to support in vivo safety assessment. To this end, we will employ a systems biology approach to comprehensively reveal the changes in the mucosal environment that may occur upon rectal administration of GRFT and GRFT combination gels. The induction of innate and adaptive immune responses in the mucosal and systemic immune compartments will be assessed using proteomic techniques. We will also use highly sensitive immunohistochemistry techniques to compare the number and location of HIV target cells, and epithelial junction proteins in rectal tissue. Additionally, the structure of rectal microbiota throughout the course of GRFT and combination gel treatment will be monitored by barcoded 16S rRNA genes sequencing to reveal the effect of microbicides formulation on the taxonomic structure of the rectal microbiota.